Place sugar, zest and raspberries into Thermo bowl and cook 10 min/100ºC/speed 2. Cool.
Add juice and yeast and stir 5 sec/speed 8. Strain through fine sieve into sterilised bottles and leave out of the fridge for 2 days until bubbles start to accumulate. Refrigerate and serve with more raspberries and lime slices to taste. It can also be diluted with sparkling water if needed.